point. In the absence of a foreign body on which droplets or crystals can nucleate, the relative humidity can exceed 100%, in which case the air is said Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the naked eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depends on the temperature and pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air. A r where Ps is the saturation pressure of water at temperature T1. Relative humidity varies with any change in the temperature or pressure of the air: colder air can contain less vapour, and water will tend to condense out of the air more at lower temperatures. So changing the temperature of air can change the relative humidity, even when the specific humidity remains constant. If two parcels of air have the same specific humidity and temperature but different pressures, the parcel at the higher pressure will have the higher relative humidity. Cooling air increases the relative humidity. If the relative humidity rises to 100% (the dew point) and there is an available surface or particle, the water vapour will condense into liquid or deposit into ice. Likewise, warming air decreases the relative humidity. Warming some air containing a fog may cause that fog to evaporate, as the droplets are prone to total evaporation due to…